In recent years, various battery-operable electronic devices such as clamshell personal computers, tablet personal computers, and smartphones are used. Such an electronic device generally includes an interface function to transmit/receive data with an external device. As an interface standard, Universal Serial Bus (USB) standard is well-known. Through an interface conforming to the USB standard, not only data but also power can be transferred. For example, when an AC adapter is, as an external device, connected to the electronic device, the battery thereof can be charged with power from the AC adapter.
When an AC adapter is connected to an electronic device with a battery which has died, components in the electronic device are activated with power from the AC adapter, and charging of the battery is started. However, charging of battery may not proceed because of delays in activation times between the components, for example.